個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外，由(you)電(dian)(dian)(dian)池(chi)提供的安全信(xin)號指示(shi)電(dian)(dian)(dian)池(chi)是(shi)否(fou)呈現(xian)在系統中和(he)是(shi)否(fou)有熱引(yin)起的告警或在其他系統失(shi)效時是(shi)否(fou)電(dian)(dian)(dian)池(chi)失(shi)效。SBS顯著特點(dian)是(shi)安全、使用容易和(he)兼(jian)容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太(tai)熱，則(ze)充(chong)電也將終(zhong)止。

　　SMBus 為(wei)(wei)系(xi)統和電(dian)(dian)源(yuan)管理這(zhe)樣的(de)(de)(de)(de)(de)任(ren)務(wu)提供(gong)了一(yi)條控(kong)制(zhi)總(zong)線，使用 SMBus 的(de)(de)(de)(de)(de)系(xi)統，設(she)(she)備之間發送和接(jie)(jie)收消息(xi)都是通過(guo) SMBus，而不(bu)是使用單獨的(de)(de)(de)(de)(de)控(kong)制(zhi)線，這(zhe)樣可以(yi)節省設(she)(she)備的(de)(de)(de)(de)(de)管腳數(shu)。 　　使用 SMBus，設(she)(she)備還可以(yi)提供(gong)它(ta)(ta)(ta)的(de)(de)(de)(de)(de)生產信(xin)(xin)息(xi)，告訴系(xi)統它(ta)(ta)(ta)的(de)(de)(de)(de)(de)型號，部件號等(deng)，針對掛起(qi)事件保存(cun)它(ta)(ta)(ta)的(de)(de)(de)(de)(de)狀態，報告不(bu)同類別的(de)(de)(de)(de)(de)錯誤，接(jie)(jie)收控(kong)制(zhi)參數(shu)，并返回它(ta)(ta)(ta)的(de)(de)(de)(de)(de)狀態等(deng)。 　　SMBus器(qi)件存(cun)在現(xian)有7層(ceng)(ceng)OSI網絡(luo)模型中的(de)(de)(de)(de)(de)前(qian)3層(ceng)(ceng)，即(ji)物理層(ceng)(ceng)，數(shu)據鏈路(lu)層(ceng)(ceng)和網絡(luo)層(ceng)(ceng)。 　　SMBus最初的(de)(de)(de)(de)(de)目的(de)(de)(de)(de)(de)是為(wei)(wei)智能電(dian)(dian)池，充電(dian)(dian)電(dian)(dian)池和與其他系(xi)統通信(xin)(xin)的(de)(de)(de)(de)(de)微控(kong)制(zhi)器(qi)之間的(de)(de)(de)(de)(de)通信(xin)(xin)鏈路(lu)而定義(yi)的(de)(de)(de)(de)(de)。SMBus也被(bei)用來連(lian)接(jie)(jie)各種設(she)(she)備，包括電(dian)(dian)源(yuan)相關設(she)(she)備，系(xi)統傳感器(qi)，EEPROM通訊設(she)(she)備等(deng)等(deng)。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范的全部安全要求，包括3分(fen)鐘定時器(qi)（保(bao)護(hu)SMBus通信換效(xiao)和(he)喚(huan)醒模式期間(jian)鋰離子(zi)電池過充電）。硬件(jian)可(ke)編程(cheng)電注和(he)電壓限(xian)制提供另外(wai)等(deng)級保(bao)護(hu)，這種保(bao)護(hu)由(you)失效(xiao)軟件(jian)不可(ke)能改(gai)變(bian)。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控制器(qi)，兩(liang)個(ge)控制充電(dian)器(qi)參量(liang)的10位DAC，一(yi)個(ge)熱敏電(dian)阻安全信號(hao)譯碼(ma)器(qi)，硬(ying)件電(dian)壓和電(dian)流限(xian)制譯碼(ma)器(qi)和一(yi)個(ge)SMBus控制器(qi)單元（見圖1）。

 智能電池(chi)或系統(tong)控制器通過SMBus接(jie)口命令(ling)對(dui)恒(heng)漢(han)和恒(heng)壓限值進行編程。降壓變壓器用N-溝(gou)MOSFET做為開關，使成(cheng)本降低、高效率(lv)工作(zuo)。熱敏電阻安全(quan)檢測(ce)電路檢測(ce)電池(chi)存在或確定電池(chi)溫(wen)度是否允許(xu)安全(quan)充電。

當(dang)通過(guo)SMBus傳輸接收(shou)恒(heng)流(liu)(liu)(liu)(liu)(liu)(liu)(liu)值(zhi)(zhi)時(shi)(shi)，它被RILIMIT定標和限制(zhi)到(dao)低(di)于編程(cheng)值(zhi)(zhi)。此修正值(zhi)(zhi)編程(cheng)電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)DAC，設置DC充電電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)。電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)DAC是10位△∑DAC，當(dang)希(xi)望充電電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)時(shi)(shi)，它從PROG引(yin)腳吸收(shou)電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)（見(jian)圖2）。放(fang)大器PROG引(yin)腳吸收(shou)電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)（見(jian)圖2）。放(fang)大器CAI感測RSENSE上的壓(ya)降并使此電壓(ya)跨接到(dao)RS2（200Ω）；流(liu)(liu)(liu)(liu)(liu)(liu)(liu)經RS2的電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)通過(guo)電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)鏡像(xiang)做(zuo)為PROG引(yin)腳上的上接電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)。流(liu)(liu)(liu)(liu)(liu)(liu)(liu)經RS2電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)與來自PROG引(yin)腳電流(liu)(liu)(liu)(liu)(liu)(liu)(liu)相匹(pi)配由CA2實現(xian)恒(heng)流(liu)(liu)(liu)(liu)(liu)(liu)(liu)工作。由于DAC輸出是一串脈沖(chong)，所以需要(yao)平滑電容器對脈沖(chong)濾波(bo)使其變為DC。

  LTC1759需(xu)要兩個電(dian)源(yuan)。PWM電(dian)路(lu)(lu)在墻(qiang)式(shi)適配(pei)器(qi)電(dian)源(yuan)斷開時(shi)(shi)直接通過Vcc引腳運行(xing)，邏輯功(gong)能(neng)運行(xing)與VDD電(dian)源(yuan)無(wu)關。PWM電(dian)路(lu)(lu)在去掉(diao)AC電(dian)源(yuan)時(shi)(shi)能(neng)進入40μA微功(gong)率停(ting)機模式(shi)，使邏輯和(he)SMBus工作能(neng)保持運行(xing)，這是Intel ACPI標準所需(xu)要的(de)。這種分離電(dian)源(yuan)也使邏輯和(he)SMBus能(neng)根(gen)據系統設計為員的(de)需(xu)要運行(xing)在3V和(he)5V.為使LTC1759邏輯功(gong)耗最小，邏輯電(dian)流由(you)時(shi)(shi)鐘電(dian)路(lu)(lu)激勵，時(shi)(shi)鐘電(dian)路(lu)(lu)當無(wu)動(dong)作時(shi)(shi)停(ting)機并蘇醒服務于SMBus動(dong)作或產生(sheng)中斷。一旦請(qing)求服務，LTC1759便返回到休眠。

　　當(dang)去掉AC電源或去掉電池時，通(tong)(tong)過CHGEN-SDB引腳組合發(fa)生PWM停機(ji)。LTC1759通(tong)(tong)過DCDIV通(tong)(tong)腳檢測AC損耗(hao)。閾值通(tong)(tong)常設(she)置恰(qia)好(hao)低于墻(qiang)式(shi)適(shi)配的最小有效電壓。AC電源狀態(tai)通(tong)(tong)過SMBus可由系(xi)統(tong)讀出(chu)。UV引腳只用于置PWM電路進入微功率停機(ji)狀態(tai)，它直接連到墻(qiang)式(shi)適(shi)配器電源。

　　在設計中電感(gan)器(qi)選擇(ze)不(bu)是(shi)關鍵，這是(shi)因為(wei)充(chong)電器(qi)的環路響應在意(yi)地設置很慢。實際的低限值(zhi)(zhi)為(wei)15μH左右(you)，低值(zhi)(zhi)電感(gan)器(qi)將(jiang)產生較高的紋波電流，在輸出(chu)需要較低ESR電容器(qi)。

　　輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的選(xuan)(xuan)擇(ze)對(dui)ESR（等(deng)效串聯電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)）不是很苛刻，但必須(xu)處理來自(zi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的所有紋(wen)波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。不用(yong)(yong)(yong)(yong)考慮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的紋(wen)波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，因為(wei)(wei)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)有效阻(zu)抗遠(yuan)遠(yuan)大(da)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感器(qi)(qi)的ESR。很多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)組具有內部串聯保護MOSFET，這提(ti)高(gao)了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)ESR。在(zai)(zai)多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)配置中也有與(yu)(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)串聯的功率路由MOSFET，進一(yi)步增加了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)ESR。從充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)觀點，輸(shu)(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)ESR可高(gao)達1Ω，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)選(xuan)(xuan)擇(ze)范(fan)圍寬(kuan)。當采用(yong)(yong)(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)負載(zai)時(shi)，可能會(hui)發生某(mou)種不穩定(ding)(ding)(ding)性(xing)。增加300Ω電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)與(yu)(yu)PROG引腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)串聯或在(zai)(zai)輸(shu)(shu)(shu)出(chu)(chu)(chu)置10μF電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)能改善穩定(ding)(ding)(ding)性(xing)。在(zai)(zai)輸(shu)(shu)(shu)出(chu)(chu)(chu)不需要(yao)用(yong)(yong)(yong)(yong)陶瓷(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)，因為(wei)(wei)在(zai)(zai)很輕(qing)負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)聲頻下開關(guan)變換器(qi)(qi)變得不連接和在(zai)(zai)下降周期開始時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)會(hui)造成噪聲，應(ying)該采用(yong)(yong)(yong)(yong)鉭電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)。輸(shu)(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)選(xuan)(xuan)擇(ze)由充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)輸(shu)(shu)(shu)入(ru)紋(wen)波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)（一(yi)般為(wei)(wei)最大(da)輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的1/2）決定(ding)(ding)(ding)。對(dui)于4A充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)建議用(yong)(yong)(yong)(yong)22μF（50V）陶瓷(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)(qi)，它一(yi)般可處理2A紋(wen)波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。

　　從電(dian)(dian)(dian)(dian)池(chi)到(dao)墻(qiang)式適(shi)配(pei)器(qi)的(de)電(dian)(dian)(dian)(dian)流(liu)保護由P-溝MOSFET（Q1）提供。電(dian)(dian)(dian)(dian)壓(ya)(ya)比較器(qi)監控(kong)跨接在MOSFET上的(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)而且當墻(qiang)式適(shi)配(pei)降到(dao)電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)之上小(xiao)于200mV時關(guan)閉MOSFET。盡(jin)管價廉的(de)二(er)極(ji)管可(ke)用于替代(dai)以(yi)MOSFET，但(dan)MOSFET只增加100mV到(dao)0.4V低(di)壓(ya)(ya)差工作模式而不產生(sheng)額外的(de)熱量(liang)。在沒有(you)電(dian)(dian)(dian)(dian)池(chi)起動時間，采(cai)用MOSFET附加二(er)極(ji)管使墻(qiang)式適(shi)配(pei)器(qi)電(dian)(dian)(dian)(dian)源能達到(dao)Vcc引腳并(bing)為PWM控(kong)制電(dian)(dian)(dian)(dian)路供電(dian)(dian)(dian)(dian)。

　　主要(yao)的補償(chang)是(shi)d PROG引腳上進行；然而DAC脈(mo)沖濾波要(yao)求(qiu)確定電(dian)容(rong)(rong)器(qi)有(you)效值。脈(mo)沖紋波電(dian)流(liu)必須(xu)小平200mV或環路起(qi)伏（在輕載充電(dian)電(dian)流(liu)時出(chu)現的環路不穩定性）。Vc引腳電(dian)容(rong)(rong)器(qi)的主要(yao)功能(neng)(neng)是(shi)提供自啟動支持。必須(xu)有(you)一個1.5K電(dian)阻(zu)器(qi)與(yu)Vc引腳電(dian)容(rong)(rong)器(qi)串聯以能(neng)(neng)恰當停機。

　　從熱觀(guan)點考慮，輸(shu)出(chu)電(dian)(dian)(dian)壓在電(dian)(dian)(dian)池溫度充電(dian)(dian)(dian)范(fan)圍內保持大約0.5%精度。精度越高，電(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)容量就(jiu)越大，而更重(zhong)要是(shi)在電(dian)(dian)(dian)池中與電(dian)(dian)(dian)壓基(ji)充電(dian)(dian)(dian)終端(duan)電(dian)(dian)(dian)路有關的(de)問題就(jiu)會更少。

　　關于(yu)SMBus加(jia)速泵，AC適(shi)配電流(liu)限制，安全(quan)信號感(gan)測，安全(quan)電壓(ya)和電流(liu)范圍(wei)設(she)計等問題在此就不一一詳述(shu)。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。